Hi. A couple of weeks ago my water supplier have changed my water meter from a mechanical type to a Kamstrup Multical 21 with IR port. The manual for the water meter says that the water meter can communicate with the Kamstrup KMP protocol, but no further information is described.

A couple of years ago I was lucky to get my hand on a description of the KMP protocol for my Kamstrup Multical 601. I builded my own IR-sensor and wrote some software for the Arduino, and it has been working without problems ever since.

I want to do the same with the water meter, but untill now I have had no success. I have tried to use the same IR-sensor and the same software. Only change is that I have tried to change the address for the water meter, and I have tried with all adresses from 0 to 255 (8 bit address value is used), but the water meter does not seem to answer my requests.

Is there anyone who have had success reading data from a Multical 21 who can help me?

Could it be that the KMP protocol is different between the Multical 21 and the Multical 601?

The manual for the Multical 21 says that the optical port on the meter is normally deactivated and will be activated 4 seconds after a magnetical IR-sensor have been placed on the meter. Could it be that the magnet in the original sensor is the one that will activated the port?

The Multical 601 worked without a magnet, and I don't have any magnets lying agound to test with. I guess this will be the next thing I will try to test.